Pharmacokinetics, Safety, and Tolerability of Single Dose Intravenous (ZTI-01) and Oral Fosfomycin in Healthy Volunteers [PublishAheadOfPrint]

The pharmacokinetics, safety, and tolerability of intravenous (IV) fosfomycin disodium (ZTI-01) and oral fosfomycin tromethamine were evaluated after a single dose in 28 healthy adult subjects. Subjects received a single 1 hour IV infusion of 1 g and 8 g fosfomycin disodium and a single dose of 3 g oral fosfomycin tromethamine in a phase I, randomized, open-label, three-period crossover study. Serial blood and urine samples were collected before and up to 48 hours after dosing. The mean pharmacokinetic parameters ± standard deviations of fosfomycin in plasma after 1 g and 8 g IV were: C_max= 44.3 ± 7.6 and 370 ± 61.9 μg/mL, T_max= 1.1 ± 0.05 and 1.08 ± 0.01 h, V_d= 29.7 ± 5.7 and 31.5 ± 10.4 liters, CL= 8.7 ± 1.7 and 7.8 ± 1.4 liters/h, CL_R= 6.6 ± 1.9 and 6.3 ± 1.6 liters/h, AUC_0-= 120 ± 28.5 and 1060 ± 192 μg⋅h/mL, and t_1/2= 2.4 ± 0.4 and 2.8 ± 0.6 h, respectively. After oral administration the parameters were: C_max= 26.8 ± 6.4 μg/mL, T_max= 2.25 ± 0.4 h, V_d/F= 204 ± 70.7 liters, CL/F= 17 ± 4.7 liters/h, CL_R= 6.5 ± 1.8 liters/h, AUC_0-= 191 ± 57.6 μg⋅h/mL, and t_1/2= 9.04 ± 4.5 h, respectively. The percent relative bioavailability of orally administered fosfomycin was 52.8% in relation to the 1 g IV dose. Approximately 74% and 80% of the 1 g and 8 g IV doses were excreted unchanged in the urine by 48 hours, compared to 37% after oral administration, with the majority of this excretion occurring by 12 hours regardless of dosage form. No new safety concerns were identified during this study. The results of this study support further investigation of IV fosfomycin in the target patient population, including patients with complicated urinary tract infections and pyelonephritis.

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